Meiosis and Sexual Reproduction

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meiosis
cell division that produces gametes; 2n->n; occurs in gonads; cell divides twice and produce 4 daughter cells; daughter cells are NOT IDENTICAL to parent (diploid-> monoploid)
gamete
sex cell that has half the number of chromosomes
diploid
containing two complete sets of chromosomes
monoploid (haploid)
having a single set of unpaired chromosomes
meiosis I
synapsis, crossing over, disjunction
Meiosis II
; each daughter cell divides again w no replication of chromosomes; results in 4 cells w half the #; daughter cells are not identical
Synapsis
tetrad; crossing over, genetic material is exchanged; disjunction, tetrads separate
tetrad
homologous chromosomes join
crossing over
tetrads twist around each other and exchange genetic material
disjunction
tetrads separate
embryonic germ layers
ectoderm, mosoderm, endoderm
ectoderm
nervous system; skin
mesoderm
muscles and skeleton; circulatory and excretory; reproductive
endoderm
digestive and respiratory; liver and pancreas
gametogenesis
the production of gametes by meiosis
spermatogenesis
the production of 4 sperm cells w half the # of chromosomes; cytoplasm divides equally
oogenesis
the production of one egg cell and 3 polar bodies; cytoplasm divides UNequally
sperm
mobile; small; 1/2 the # of chromosomes; head and midpiece
head (sperm)
contains nucleus (genetic material)
midpiece (sperm)
contains mitochondria
egg
cannot move; larger than sperm; 1/2 the # of chromosomes
fertilization
gametes join; restores species chromosome #; sperm joins w the egg in the oviduct (humans); n+n=2n
internal fertilization
terrestrial organisms; occurs inside female; low # of eggs; gametes are more protected; mammals, reptiles, birds
external fertilization
aquatic organisms; occurs outside female; high # of eggs; gametes are NOT protected; many are lost, die, eaten; fish and amphibians
differentiation
cells specialize and certain genes are activated to produce proteins that are related to the cell function
scrotum
contains testes; keeps sperm 2-3 degrees lower than body temperature
testes
male gonads; meiosis; produces sperm and testosterone
epididymis
stores and matures sperm
vas deferens
brings sperm from testes to the urethra
cowpers gland, seminal vesicles, prostate
produce fluid for semen
urinary bladder
stores urine
urethre
transports urine, semen out of body
penis
adaptation for internal fertilization
ovary
female gonad; meiosis; (2n->n); eggs are produced; estrogen and progesterone;
estrogen and progesterone
responsible for secondary sex characteristics
oviduct
fallopian tube; internal fertilization occurs here
uterus
embryo implants and develops (placenta); mitosis and differentiation
vagina
birth canal
cervix
opening to uterus
external development
chorion; amniotic fluid; allantois; embryo; air space; yolk sac; yolk; albumin
chorion
gas exchange
amniotic fluid
cushions and protects
allantois
gas exchange and storage
embryo
developing chick
air space
space between the shell and chorion
yolk sac
surrounds the yolk
yolk
nutrients for developing embryo
albumin
protein that surrounds embryo
placental mammal
internal development
placenta
materials are exchanged between mother and fetus; diffusion of O2 and CO2, nutrients, wastes; maternal and embryonic material; develops only during pregnancy
umbilical cord
transports nutrients and oxygen to the fetus; takes waste and CO2 away from the fetus
amniotic sac
surrounds and protects the embryo; contains amniotic fluid; shock absorber
identical twins
zygote divides into 2 embryos; embryos have the same DNA; develop inside the SAME amniotic sac
fraternal twins
two different eggs are fertilized by two different zygotes; embryos have different DNA; separate sacs
c section (caesarean section)
surgical procedure to deliver a baby from a mother
avoid (during pregnancy)
sushi (raw meat), cigarettes, radiation, alcohol, tuna
gestation
fertilization to birth (9 months)
in-vitro
sperm and egg are joined outside the body and the zygote is implated
surrogate
zygote is implanted into the uterus of another woman
Labor (stages of child birth)
1. contractions of the uterus
2. bloody show
3. water breaks
4. cervix dilates (10 cm.)
5. fetus passes through the birth canal
6. after birth= placenta and umbilical cord
non placental (mammals)
mammals in which no placenta forms during development
egg laying (mammals)
spiny anteaters; duckbill platypus
marsupials
have a pouch or the fetus completes development attached to mammary glands
human menstrual cycle
28 days; hormone controlled; prepares body for pregnancy at each month; begins at puberty; ends at menopause; temporarily stops during pregnancy
stages of menstrual cycle
follicle; ovulation; corpus luteum; menstruation
follicle
occurs days 1 through 14; egg matures in ovary
ovulation
occurs on day 14; egg is released from ovary
corpus luteum
occurs days 15 through 28; uterine lining thickens
menstruation
occurs days 1 through 5;uterine lining sheds